GROUP 1 : Gabriel, Darren, Yi Fan
TASK 1:
This is a table showing the frequency percentage of each letter in the English alphabet.
Letter
Percentage
Letter
Percentage
a
8.2
n
6.7
b
1.5
o
7.5
c
2.8
p
1.9
d
4.3
q
0.1
e
12.7
r
6.0
f
2.2
s
6.3
g
2.0
t
9.1
h
6.1
u
2.8
i
7.0
v
1.0
j
0.2
w
2.4
k
0.8
x
0.2
l
4.0
y
2.0
m
2.4
z
0.1
Symbol
|
Δ
Occurence
5
1
trequency/text
6.2/ I
1.2
Symbol Occurrence
f
5
4
trequency/text
6.2/ R
2.5
Ø
O
8
C
6
9
3
3
4
4
7.4/ N
11.1/ A
3.7
3.7
4.9/B
4.9/H
M
9
q
1
1
11
2
10
1
1.2
1.2/ Z
13.6/ E
2.5/ L
12.3 / T
1.2

2
5
2.5/ G
6.2/ O
1
2
1.2
2.5




TN nOTHNO*
Since this is the Anthony babbington’s plot, we can presume that the second word is “anthony”, so we
start fine-tuning the links. O and N should be swapped with each other.
TO nNTHONY
Now we make another guess- after anthony, it should be babbington as that is his name.
TO ANTHONY BABBINGTON.
Now we match babbington to its symbols.
TO ANTHONY BABBINGTON
I AG*EE THAT *O*
*nN **R*ER **EEN
E*I*ABETH nT T*E
EAR**IE*T TI*E
*RO* *ARY
Now we fill in the fourth line, ELIZABETH
TO ANTHONY BABBINGTON
I AGREE THAT YOU CAN MURDER QUEEN ELIZABETH AT THE EARLIEST TIME
FROM MARY (DECRYPTED!)
TASK 2:
The Vigenère cipher is a method of encrypting alphabetic text by using a series of
different Caesar ciphers which is a simple form of polyalphabetic substitution. So it is a
method which always switching the code. It is hard to be cracked because each alphabet is
represented by 26 alphabets.
To encode a message you should set a table like this:
Secondly, the party which sending the message chooses a keyword and repeats it until it
becomes the length of the plaintext. For example, the message is: FREQUENCY
ANALYSIS
, which is 17 alphabets. Then the party chooses a keyword like: BEDOK. Then repeats
the word: BEDOKBEDOKBEDOKBE.
So it becomes:
FREQUENCY ANALYSIS
BEDOKBEDO KBEDOKBE
After that you shall find your new alphabet for your message on the table which
you set just now. This is done by looking at the letter in row B and column F of the
Vigenère square, namely G. Similarly, for the second letter of the plaintext, the second letter
of the key is used; the letter at row E and column R is V.
Therefore you will get a ciphertext: GVHEEFRFM KOEOMCJW.
(2)The message is: TO ANTHONY BABBINGTON
I AGREE THAT YOU CAN MURDER QUEEN ELIZABETH AT THE EARLIEST TIME
FROM MARY.
The key is: CIPHER
So it becomes: VW PUXYQVN IESDQCNXFP
Q PNVVG BWHX PQC RHR DWZSLV HWMTU ICKHPIIKJ II ALV GIGSMVUB IPQV
HZDT QRTG.
TASK 3:
We have to decrypt this encrypted text: mxftagstymzkarftqyqeemsqeiqeqzphumqymuxmdqfduhumx
ftqdqmdqfuyqeitqziqimzffaymwqegdqftmfzaazqomzezaabaz
itmfiqmdqemkuzsazqimkarqzodkbfuzsqymuxeuefageqmearfimdq
bmowmsqwzaizmebdqffksaapbduhmokituotoaynuzqeqxqyqzfe
aroazhqzfuazmxodkbfasdmbtkmzpbgnxuowqkqzodkbfuazufime
odqmfqpnkptuxubluyyqdymzzmzpimeuzufumxxkarrqdqprdqqaz
ftquzfqdzqfpueogeeuazsdagbgeqzqfftqbsbearfimdqsqzqdmfqe
mdmzpaywqknmeqpazftqyahqyqzfearkagdyageqmzpftqimkkag
fkbqftuedmzpaywqkueftqzgeqpfaqzodkbfkagdyqeemsqftqzqjf
efmsquefageqbgnxuowqkqzodkbfuazngfuzefqmpargeuzsftuefa
qzodkbfftqyqeemsqftqdmzpaywqkgeqpuzftqbdqhuageefmsque
qzodkbfqpgeuzskagdbgnxuowqkmzpeqzfmxazsiuftftqyqeemsq
ituottmenqqzqzodkbfqpgeuzsftqdmzpaywqkitqzftqdqoubuqzf
dqoquhqekagdyqeemsquzefqmpargeuzsftqbduhmfqwqkfa
pqodkbfftqyqeemsqftqkpqodkbfftqdmzpaywqkmzpftqzgeqftmf
fapqodkbfftqmffmotqpyqeemsqftqbgnxuomfuazarbsbaz
geqzqfemiluyyqdymzzegnvqoffamoduyuzmxuzhqefusmfuaznk
ftqgesahqdzyqzfituotoxmuyqpftmfbgnxuetuzsbsbuzftueimk
huaxmfqpgeqjbadfdqefduofuazeradodkbfasdmbtuoearfimdq
Now we carry out a frequency analysis test of the alphabets in the encrypted texts.
a : 62 ... 6.2 %
b : 36 ... 3.6 %
c : 0 ... 0.0 %
d : 52 ... 5.2 %
e : 70 ... 7.0 %
f : 94 ... 9.4 %
g : 31 ... 3.1 %
h : 11 ... 1.1 %
i : 21 ... 2.1 %
j : 2 ... 0.2 %
k : 39 ... 3.9 %
l : 2 ... 0.2 %
m : 73 ... 7.3 %
n : 12 ... 1.2 %
o : 34 ... 3.4 %
p : 29 ... 2.9 %
q : 135 ... 13.6 %
r : 14 ... 1.4 %
s : 29 ... 2.9 %
t : 46 ... 4.6 %
u : 65 ... 6.5 %
v : 1 ... 0.1 %
w : 12 ... 1.2 %
x : 18 ... 1.8 %
y : 31 ... 3.1 %
z : 77 ... 7.7 %
The most common 3-alphabets run-on sentence is FTQ. We found this out after analyzing the text.
Also, we know that Q is the most frequently seen word in the encrypted text, thus we match it to the
letter E. Knowing these things, we now can make an intelligent guess that FTQ actually stands for THE.
So we replace FTQ with THE.
From here, we can actually realize that when we match FTQ with THE, the alphabets starting from F to T
then to Q is actually in alphabetical order when you match it with THE. So now we start replacing the
alphabets in the encrypted text alphabetically. We start by matching F to T, then G to U, H to V, and so
on and so forth, until we have completed replacing every letters.
Finally, we get the decrypted text:
ALTHOUGHMANYOFTHEMESSAGESWESENDVIAEMAILARETRIVIAL
THEREARETIMESWHENWEWANTTOMAKESURETHATNOONECANSNOOPON
WHATWEARESAYINGONEWAYOFENCRYPTINGEMAILSISTOUSEASOFTWARE
PACKAGEKNOWNASPRETTYGOODPRIVACYWHICHCOMBINESELEMENTS
OFCONVENTIONALCRYPTOGRAPHYANDPUBLICKEYENCRYPTIONITWAS
CREATEDBYDHILIPZIMMERMANNANDWASINITIALLYOFFEREDFREEON
THEINTERNETDISCUSSIONGROUPUSENETTHEPGPSOFTWAREGENERATES
ARANDOMKEYBASEDONTHEMOVEMENTSOFYOURMOUSEANDTHEWAYYOU
TYPETHISRANDOMKEYISTHENUSEDTOENCRYPTYOURMESSAGETHENEXT
STAGEISTOUSEPUBLICKEYENCRYPTIONBUTINSTEADOFUSINGTHISTO
ENCRYPTTHEMESSAGETHERANDOMKEYUSEDINTHEPREVIOUSSTAGEIS
ENCRYPTEDUSINGYOURPUBLICKEYANDSENTALONGWITHTHEMESSAGE
WHICHHASBEENENCRYPTEDUSINGTHERANDOMKEYWHENTHERECIPIENT
RECEIVESYOURMESSAGEINSTEADOFUSINGTHEPRIVATEKEYTO
DECRYPTTHEMESSAGETHEYDECRYPTTHERANDOMKEYANDTHENUSETHAT
TODECRYPTTHEATTACHEDMESSAGETHEPUBLICATIONOFPGPON
USENETSAWZIMMERMANNSUBJECTTOACRIMINALINVESTIGATIONBY
THEUSGOVERNMENTWHICHCLAIMEDTHATPUBLISHINGPGPINTHISWAY
VIOLATEDUSEXPORTRESTRICTIONSFORCRYPTOGRAPHICSOFTWARE
Next, we add in the spaces.
ALTHOUGH MANY OF THE MESSAGES WE SEND VIA EMAIL ARE TRIVIAL THERE ARE TIMES WHEN WE
WANT TO MAKE SURE THAT NO ONE CAN SNOOP ON WHAT WE ARE SAYING ONE WAY OF ENCRYPTING
EMAILS IS TO USE A SOFTWARE PACKAGE KNOWN AS PRETTY GOOD PRIVACY WHICH COMBINES
ELEMENTS OF CONVENTIONAL CRYPTOGRAPHY AND PUBLIC KEY ENCRYPTION IT WAS CREATED BY
DHILIP ZIMMERMANN AND WAS INITIALLY OFFERED FREE ON THE INTERNET DISCUSSION GROUP USE
NET THE PGP SOFTWARE GENERATES A RANDOM KEY BASED ON THE MOVEMENTS OF YOUR MOUSE
AND THE WAY YOU TYPE THIS RANDOM KEY IS THEN USED TO ENCRYPT YOUR MESSAGE THE NEXT
STAGE IS TO USE PUBLIC KEY ENCRYPTION BUT INSTEAD OF USING THIS TO ENCRYPT THE MESSAGE THE
RANDOM KEY USED IN THE PREVIOUS STAGE IS ENCRYPTED USING YOUR PUBLIC KEY AND SENT ALONG
WITH THE MESSAGE WHICH HAS BEEN ENCRYPTED USING THE RANDOM KEY WHEN THE RECIPIENT
RECEIVES YOUR MESSAGE INSTEAD OF USING THE PRIVATE KEY TO DECRYPT THE MESSAGE THEY
DECRYPT THE RANDOM KEY AND THEN USE THAT TO DECRYPT THE ATTACHED MESSAGE THE
PUBLICATION OF PGP ON USE NET SAW ZIMMERMANN SUBJECT TO A CRIMINAL INVESTIGATION BY
THE US GOVERNMENT WHICH CLAIMED THAT PUBLISHING PGP IN THIS WAY VIOLATED US EXPORT
RESTRICTIONS FOR CRYPTOGRAPHIC SOFTWARE
We have got the text in plain English now =)
Task 3:
MXtdnGSdYMZKnRtdeYeooMSeoIeoeZPHiMeYMiXMsetsiHiMX
tdeseMsetiYeoIdeZIeIMZttnYMWeorsetdMtZnnZeOMZoZnnhnZ
IdMtIeMseoMKiZSnZeIMKnReZOsKhtiZSeYMiXoiotnroeMonRtIMse
hMOWMSeWZnIZMohsettKSnnPhsiHMOKIdiOdOnYNiZeoeXeYeZto
nROnZHeZtinZMXOsKhtnSsMhdKMZPhrNXiOWeKeZOsKhtinZitIMo
OseMtePNKPdiXihLiYYesYMZZMZPIMoiZitiMXXKnRResePRseenZ
tdeiZtesZetPioOrooinZSsnrhroeZettdehShonRtIMseSeZesMteo
MsMZPnYWeKNMoePnZtdeYnHeYeZtonRKnrsYnroeMZPtdeIMKKnr
tKhetdiosMZPnYWeKiotdeZroePtneZOsKhtKnrsYeooMSetdeZeJt
otMSeiotnroehrNXiOWeKeZOsKhtinZNrtiZoteMPnRroiZStdiotn
eZOsKhttdeYeooMSetdesMZPnYWeKroePiZtdehseHinrootMSeio
eZOsKhteProiZSKnrshrNXiOWeKMZPoeZtMXnZSIitdtdeYeooMSe
IdiOddMoNeeZeZOsKhteProiZStdesMZPnYWeKIdeZtdeseOihieZt
seOeiHeoKnrsYeooMSeiZoteMPnRroiZStdehsiHMteWeKtn
PeOsKhttdeYeooMSetdeKPeOsKhttdesMZPnYWeKMZPtdeZroetdMt
tnPeOsKhttdeMttMOdePYeooMSetdehrNXiOMtinZnRhShnZ
roeZetoMILiYYesYMZZorNVeOttnMOsiYiZMXiZHeotiSMtinZNK
tderoSnHesZYeZtIdiOdOXMiYePtdMthrNXiodiZShShiZtdioIMK